The present invention relates generally to a system which can be used when an interventional procedure is being performed in a stenosed or occluded region of a blood vessel to capture embolic material that may be created and released into the bloodstream during the procedure. The system of the present invention is particularly useful when performing balloon angioplasty, stenting procedures, laser angioplasty or atherectomy in critical vessels, such as the carotid arteries, where the release of embolic debris into the bloodstream can occlude the flow of oxygenated blood to the brain or other vital organ. It is to be understood that the system and method of this invention can be used in numerous other vascular interventional procedures.
Numerous procedures have been developed for treating occluded blood vessels to allow blood to flow without obstruction. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient""s arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the size of the blood vessel.
Another procedure is laser angioplasty which utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which a cutting blade is rotated to shave the deposited plaque from the arterial wall.
In another widely practiced procedure, the stenosis can be treated by placing a device known as a stent into the stenosed region to hold open and sometimes expand the segment or blood vessel or other arterial lumen. Stents are particularly useful in the treatment or repair of blood vessels by percutaneous transluminal coronary angioplasty (PTCA), percutaneous transluminal angioplasty (PTA) or removal by atherectomy or other means. Stents are delivered in a compressed condition to the target site, and then are deployed at the target location into an expanded condition to support the vessel.
In the process of treating lesions in the blood vessels, release of plaque (embolic debris) may possibly occur during the treatment. Detached from the lesion, the embolic debris enters the bloodstream and subsequently migrate through the patient""s vasculature. Larger embolic debris can obstruct a vessel and cause ischemia, apoptosis, or vessel necrosis.
To allow the use of more aggressive treatment of vascular lesions, procedures have also been developed for capturing embolic debris flowing through the vessels with the blood. One approach involves the placement of a filter downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. The placement of a filter in the patient""s vasculature during treatment of the vascular lesion can reduce the presence of the embolic debris in the bloodstream. Such filters are usually delivered in a collapsed position through the patient""s vasculature and then expanded to trap the embolic debris. Once the procedure is completed, the filter can be collapsed, and the filter (with the trapped embolic debris) can then be removed from the vessel. While a filter can be effective in capturing embolic material, the filter still needs to be collapsed and removed from the vessel. During this procedure, it is important that the captured embolic debris remain trapped within this filter so that particles are not released back into the body vessel. Additionally, the recovery apparatus should be relatively flexible to avoid straightening the body vessel. Recovery devices which are too stiff can cause trauma to the vessel walls as the filter is being collapsed and removed from the vasculature.
There is a need in the art for an apparatus and method which can collapse a deployed filter containing captured embolic material for removal from the vasculature. Such an apparatus and method should be capable of being delivered through tortuous anatomy to the desired treatment site, and avoid straightening of the vasculature during delivery. Such an apparatus and method should be easy and safe to deploy, and be easily removed from the vasculature with minimal adverse impact or immunological response to the patient.
The present invention is directed to embolic protection systems having reduced stiffness characteristics. The recovery system of the present invention can be used to recovery an embolic protection device which generally includes a guide wire having a distal end and an expandable filter located near the distal end of the guide wire. The recovery system utilizes an inner catheter which is capable of being introduced over the guide wire, along with a recovery sheath that extends co-axially over the inner catheter. The inner catheter is capable of being loaded inside a lumen of the recovery sheath. In use, a distal portion of the inner catheter extends beyond the distal end of the recovery sheath allowing the inner catheter to initially approach the expandable filter which has been deployed within the patient""s vasculature. In one aspect of the present invention, the distal portion of the inner catheter can initially extend approximately ten to fifteen centimeters, or more, beyond the distal end of the recovery sheath during initial delivery within the patient""s vasculature. Thereafter, once the inner catheter has been placed near the expandable filter, the recovery sheath can then be advanced up over the inner catheter to collapse the expandable filter as the recovery sheath advances over the expandable filter. Thus, during delivery, the composite embolic protection recovery system has reduced stiffness characteristics at the distal end since the more flexible distal portion of the inner catheter extends beyond the recovery sheath. This reduced stiffness improves tracking over the guide wire through the patient""s vasculature and also helps to avoid the tendency of curved vasculature to xe2x80x9cstraightenxe2x80x9d due to the presence of a somewhat stiff recovery sheath. In this regard, the inner catheter, which has a smaller diameter and can be more flexible by having less column strength than the recovery sheath, initially tracks through the vasculature allowing the patient""s vasculature to first conform to the inner catheter, rather than being xe2x80x9cstraightenedxe2x80x9d due to the presence of a stiffer recovery sheath. The inner catheter could also have high column stiffness, but be relatively easily bent radially, as if a polyimide were being used. Thereafter, the patient""s vasculature will be less likely to straighten as the recovery sheath is advanced over the inner catheter to collapse the expandable filter.
In one aspect of the embolic protection recovery system, the recovery sheath has greater column strength than the inner catheter. As a result, the composite recovery system has reduced stiffness characteristics at the distal end where it would be needed. This particular delivery structure which reduces stiffness helps to improve the trackability of the composite recovery system over the guide wire and through the vasculature, as well.
The method of using the embolic protection recovery system includes loading the inner catheter inside a recovery sheath, wherein the recovery sheath is initially placed over the inner catheter such that a distal portion of the inner catheter extends beyond the distal end of the recovery sheath. The inner catheter can then be introduced over the guide wire having an expanded filter located near the distal end of the guide wire; and advancing the distal end of the inner catheter to a position adjacent to the expanded filter located within the patient""s vasculature. The recovery sheath can then by advanced over the distal portion of the inner catheter and over the expanded filter in order to collapse the expanded filter. The recovery sheath, inner sheath, and collapsed filter can then be removed from the vasculature.
It is to be understood that the present invention is not limited by the embodiments described herein. The present invention can be used in arteries, veins, and other body lumens. Other features and advantages of the present invention will become more apparent from the following detailed description of the invention, when taken in conjunction with the accompanying exemplary drawings.